The Two Micron All Sky Survey (2MASS) Skrutskie, M. F; Cutri, R. M; Stiening, R ...
The Astronomical journal,
02/2006, Volume:
131, Issue:
2
Journal Article
Peer reviewed
Open access
Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imaging data covering 99.998% of the celestial sphere in the near-infrared J (1.25 mm), H (1.65 ...mm), and Ks (2.16 mm) bandpasses. Observations were conducted from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona, and Cerro Tololo, Chile. The 7.8 s of integration time accumulated for each point on the sky and strict quality control yielded a 10 s point-source detection level of better than 15.8, 15.1, and 14.3 mag at the J, H, and Ks bands, respectively, for virtually the entire sky. Bright source extractions have 1 s photometric uncertainty of <0.03 mag and astrometric accuracy of order 100 mas. Calibration offsets between any two points in the sky are <0.02 mag. The 2MASS All-Sky Data Release includes 4.1 million compressed FITS images covering the entire sky, 471 million source extractions in a Point Source Catalog, and 1.6 million objects identified as extended in an Extended Source Catalog.
We present Hubble Space Telescope/WFPC2 images of the galaxies NGC 2366, NGC 2976, NGC 4236, IC 2574, DDO 53, DDO 82, DDO 165, Holmberg I, Holmberg II, Holmberg IX, K52, K73, BK3N, Garland, and ...A0952+69 in the M 81 complex. Their true distance moduli, derived from the brightness of the tip of the red giant branch, lie in the range of 27$\fm$52 (NGC 2366) to 28$\fm$30 (DDO 165), with a median of 27$\fm$91, which is typical for other known M 81 group members. Using distances and radial velocities of about 50 galaxies in and around the M 81/NGC 2403 complex, we find the radius of the zero-velocity surface of the M 81 group to be $R_0 = (1.05\pm0.07$) Mpc, which yields a total mass $M(R_0) = (1.6\pm0.3)\times 10^{12}~M_{\odot}$ and a total mass-to-luminosity ratio $M(R_0)/L_B = (38\pm7)~M_{\odot}/L_{\odot}$. The total mass within R0 agrees well with the sum of masses estimated via the virial theorem ($1.2\times 10^{12}~M_{\odot})$ and from orbital motions $(2.0\times 10^{12}~M_{\odot})$ of companions around M 81 and NGC 2403. We suggest that most of the dark matter in the group is concentrated around the luminous matter, allowing us to explain the observed asymmetry of the peculiar motions of the M 81 companions. M 81 itself has a peculiar velocity of about 130 km s-1 with respect to the local Hubble flow, but the centroid of the M 81/NGC 2403 complex is almost at rest with respect to Hubble flow $(v_{\rm pec} < 35$ km s-1).
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Distances to nearby galaxies in Sculptor Karachentsev, I. D.; Grebel, E. K.; Sharina, M. E. ...
Astronomy and astrophysics (Berlin),
06/2003, Volume:
404, Issue:
1
Journal Article
Peer reviewed
Open access
We present an analysis of Hubble Space Telescope/WFPC2 images of nine nearby galaxies in Sculptor. We derive their distances from the luminosity of the tip of the red giant branch stars with a ...typical accuracy of ∼ 12%. Their distances are 4.21 Mpc (Sc 22), 4.92 Mpc (DDO 226), 3.94 Mpc (NGC 253), 3.40 Mpc (KDG 2), 3.34 Mpc (DDO 6), 3.42 Mpc (ESO 540-030), 4.43 Mpc (ESO 245–05), 4.27 Mpc (UGCA 442), and 3.91 Mpc (NGC 7793). The galaxies are concentrated in several spatially separated loose groups around NGC 300, NGC 253, and NGC 7793. The Sculptor galaxy complex together with the CVn I cloud and the Local Group form a 10 Mpc filament, apparently driven by the free Hubble flow.
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We present Hubble Space Telescope/WFPC2 images of seventeen dwarf galaxies in the Centaurus A group. Their distances derived from the magnitudes of the tip of the red giant branch are 5.2 Mpc ...(KK112), 3.2 Mpc (ESO 321-014), 3.5 Mpc (KK179), 3.4 Mpc (NGC 5102), 4.6 Mpc (KK200), 3.7 Mpc (ESO 324-024), 4.7 Mpc (KK208), 4.6 Mpc (ESO 444-084), 4.4 Mpc (IC 4316), 4.5 Mpc (NGC 5264), 3.6 Mpc (KK211), 3.6 Mpc (KK213), 3.4 Mpc (ESO 325-011), 3.8 Mpc (KK217), 4.0 Mpc (KK221), 4.8 Mpc (NGC 5408), and 3.6 Mpc (PGC 51659). The galaxies are concentrated in two spatially separated groups around NGC 5128 = Cen A and NGC 5236 = M 83. The Cen A group itself has a mean distance of $3.63\pm 0.07$ Mpc, a velocity dispersion of 89 km s-1, a mean projected radius of 263 kpc, an estimated orbital mass of $2.1\times 10^{12} M_{\odot}$, and an orbital mass-to-blue luminosity ratio of 64 $M_{\odot}/L_{\odot}$. For the M 83 group we derived a mean distance of $4.57\pm 0.05$ Mpc, a velocity dispersion of 62 km s-1, a mean projected radius of 142 kpc, an estimated orbital mass of $0.8\times 10^{12} M_{\odot}$, and $M_{\rm orb}/L_{\rm B} = 37~M_{\odot}/L_{\odot}$. The M 83 group moves away from the Cen A group, which yields a radius of the zero-velocity surface of the Cen A group of $R_0 < 1.26$ Mpc. The total mass within $R_0, M_0 < 2.7\times 10^{12} M_{\odot}$, agrees with the orbital mass estimate. The centroids of both the groups have very small peculiar velocities, $(+18\pm 24)$ km s-1 (Cen A) and ($-17\pm27$) km s-1 (M 83) with respect to the local Hubble flow with $H_0 = 70$ km s-1 Mpc-1.
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Local galaxy flows within 5 Mpc Karachentsev, I. D.; Makarov, D. I.; Sharina, M. E. ...
Astronomy and astrophysics (Berlin),
02/2003, Volume:
398, Issue:
2
Journal Article
Peer reviewed
Open access
We present Hubble Space Telescope/WFPC2 images of sixteen dwarf galaxies as part of our snapshot survey of nearby galaxy candidates. We derive their distances from the luminosity of the tip of the ...red giant branch stars with a typical accuracy of ~12%. The resulting distances are 4.26 Mpc (KKH 5), 4.74 Mpc (KK 16), 4.72 Mpc (KK 17), 4.66 Mpc (ESO 115-021), 4.43 Mpc (KKH 18), 3.98 Mpc (KK 27), 4.61 Mpc (KKH 34), 4.99 Mpc (KK 54), 4.23 Mpc (ESO 490-017), 4.90 Mpc (FG 202), 5.22 Mpc (UGC 3755), 5.18 Mpc (UGC 3974), 4.51 Mpc (KK 65), 5.49 Mpc (UGC 4115), 3.78 Mpc (NGC 2915), and 5.27 Mpc (NGC 6503). Based on distances and radial velocities of 156 nearby galaxies, we plot the local velocity-distance relation, which has a slope of $H_0 = 73$ km s-1 Mpc-1 and a radial velocity dispersion of 85 km s-1. When members of the M81 and Cen A groups are removed, and distance errors are taken into account, the radial velocity dispersion drops to $\sigma_{\rm v} = 41$ km s-1. The local Hubble flow within 5 Mpc exhibits a significant anisotropy, with two infall peculiar velocity regions directed towards the Supergalactic poles. However, two observed regions of outflow peculiar velocity, situated on the Supergalactic equator, are far away (~50°) from the Virgo/anti-Virgo direction, which disagrees with a spherically symmetric Virgo-centric flow. About 63% of galaxies within 5 Mpc belong to known compact and loose groups. Apart from them, we found six new probable groups, consisting entirely of dwarf galaxies.
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The very local Hubble flow Karachentsev, I. D.; Sharina, M. E.; Makarov, D. I. ...
Astronomy and astrophysics (Berlin),
07/2002, Volume:
389, Issue:
3
Journal Article
Peer reviewed
Open access
We present Hubble Space Telescope/WFPC2 images of eighteen galaxies situated in the vicinity of the Local Group (LG) as part of an ongoing snapshot survey of nearby galaxies. Their distances derived ...from the magnitude of the tip of the red giant branch are $1.92\pm0.10$ Mpc (ESO 294-010), $3.06\pm0.37$ (NGC 404), $3.15\pm0.32$ (UGCA 105), $1.36\pm0.07$ (Sex B), $1.33\pm0.08$ (NGC 3109), $2.64\pm0.21$ (UGC 6817), $2.86\pm0.14$ (KDG 90), $2.27\pm0.19$ (IC 3104), $2.54\pm0.17$ (UGC 7577), $2.56\pm0.15$ (UGC 8508), $3.01\pm0.29$ (UGC 8651), $2.61\pm0.16$ (KKH 86), $2.79\pm0.26$ (UGC 9240), $1.11\pm0.07$ (SagDIG), $0.94\pm0.04$ (DDO 210), $2.07\pm0.18$ (IC 5152), $2.23\pm0.15$ (UGCA 438), and $2.45\pm0.13$ (KKH 98). Based on the velocity-distance data for 36 nearest galaxies around the LG, we find the radius of the zero-velocity surface of the LG to be $R_0 = (0.94\pm0.10)$ Mpc, which yields a total mass $M_{\rm LG} = (1.3\pm0.3)\times 10^{12}~M_{\odot}$. The galaxy distribution around the LG reveals a Local Minivoid which does not contain any galaxy brighter than MV=-11 mag within a volume of ~100 Mpc3. The local Hubble flow seems to be very cold, having a one-dimensional mean random motion of ~30 km s-1. The best-fit value of the local Hubble parameter is $73\pm15$ km s-1 Mpc-1. The luminosity function for the nearby field galaxies is far less steep than one for members of the nearest groups.
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We derive quantitative star formation histories of the four suspected tidal dwarf galaxies in the M 81 group, Holmberg IX, BK3N, Arp-loop (A0952+69), and Garland, using Hubble Space Telescope/Wide ...Field Planetary Camera 2 images in F606W and F814W obtained as part of a Snapshot survey of dwarf galaxies in the Local Universe. We consider the spatial distribution and ages of resolved stellar populations in these dwarf irregular galaxies. We use synthetic color-magnitude diagrams to derive the ages of the major star formation episodes, star formation rates, and approximate metallicity ranges. All the galaxies show evidence of continuous star formation between about 20 and 200 Myr ago with star formation rates in the range $7.5\times10^{-3}$–$7.6\times10^{-4}~M_{\odot}$ yr-1. The metallicity of the detected stars spans a wide range, and have lower than solar abundance. A possible scenario is that all four dwarf galaxies were formed from material in the metal-poor outer part of the giant spiral galaxy M 81 after the tidal interaction between M 81, M 82, and NGC 3077 $\sim 200$ Myr ago. While we do not directly detect pronounced old stellar populations, the photometric limits of our data are such that the presence of such a population is not entirely ruled out.
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Galaxy flow in the Canes Venatici I cloud Karachentsev, I. D.; Sharina, M. E.; Dolphin, A. E. ...
Astronomy and astrophysics (Berlin),
02/2003, Volume:
398, Issue:
2
Journal Article
Peer reviewed
Open access
We present an analysis of Hubble Space Telescope/WFPC2 images of eighteen galaxies in the Canes Venatici I cloud. We derive their distances from the luminosity of the tip of the red giant branch ...stars with a typical accuracy of ~12%. The resulting distances are 3.9 Mpc (UGC 6541), 4.9 Mpc (NGC 3738), 3.0 Mpc (NGC 3741), 4.5 Mpc (KK 109), > 6.3 Mpc (NGC 4150), 4.2 Mpc (UGC 7298), 4.5 Mpc (NGC 4244), 4.6 Mpc (NGC 4395), 4.9 Mpc (UGC 7559), 4.2 Mpc (NGC 4449), 4.4 Mpc (UGC 7605), 4.6 Mpc (IC 3687), 4.7 Mpc (KK 166), 4.7 Mpc (NGC 4736), 4.2 Mpc (UGC 8308), 4.3 Mpc (UGC 8320), 4.6 Mpc (NGC 5204), and 3.2 Mpc (UGC 8833). The CVn I cloud has a mean radial velocity of $286 \pm 9$ km s-1, a mean distance of $4.1 \pm 0.2$ Mpc, a radial velocity dispersion of 50 km s-1, a mean projected radius of 760 kpc, and a total blue luminosity of $2.2 \times 10^{10} L_{\sun}$. Assuming virial or closed orbital motions for the galaxies, we estimated their virial and their orbital mass-to-luminosity ratio to be 176 and 88 $ M_{\sun}/L_{\sun} $, respectively. However, the CVn I cloud is characterized by a crossing time of 15 Gyr, and is thus far from a state of dynamical equilibrium. The large crossing time for the cloud, its low content of dSph galaxies (< 6%), and the almost “primordial” shape of its luminosity function show that the CVn I complex is in a transient dynamical state, driven rather by the free Hubble expansion than by galaxy interactions.
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We have used the ARGUS multi-object spectrometer at the CTIO 4 m Blanco telescope to obtain 2756 radial velocity measurements for 1966 individual stars in the globular cluster ω Centauri brighter ...than blue photographic magnitude of about 16.5. Of these, 1589 stars are cluster members. A comparison with two independent radial velocity studies, carried out by Suntzeff & Kraft and by Mayor et al., demonstrates that the median error of our measurements is below 2 km s-1 for the stars brighter than B-magnitude 15, which constitute the bulk of the sample. The observed velocity dispersion decreases from about 15 km s-1 in the inner few arcmin to about 6 km s-1 at a radius of 25'. The cluster shows significant rotation, with a maximum amplitude of about 6 km s-1 in the radial zone between 6' and 10'. In a companion paper by van de Ven et al., we correct these radial velocities for the perspective rotation caused by the space motion of the cluster, and combine them with the internal proper motions of nearly 8000 cluster members measured by van Leeuwen et al., to construct a detailed dynamical model of ω Centauri and to measure its distance.
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We present velocities for 230 stars in the outer parts of the globular cluster M15 measured with the Hydra multifiber spectrograph on the 3.5 m WIYN telescope. A new Bayesian technique is used for ...analyzing the data. The mean velocity of the cluster is -106.9 +/- 0.3 km/s. Rotation with an amplitude of 1.5 +/- 0.4 km/s and a position angle of 125 deg +/- 19 deg is observed, and a model including rotation is marginally favored over one without rotation. The velocity dispersion decreases from the center out to 7 arcmin and then appears to increase slightly. This behavior is strikingly different from the continued decline of velocity dispersion with increasing radius that is expected in an isolated cluster. We interpret this as an indication of heating of the outer part of M15 by the Galactic tidal field. (Author)